Once Through Steam Generator

ABSTRACT

A once-through steam generator (OTSG) creating steam from feedwater by heat provided by flue gas. Combustion air is introduced into the OTSG through an air input/output apparatus. It is then fed into a combustion system to generate the flue gas. The flue gas is then fed into a steam generation apparatus to generate steam. The flue gas is returned to the air input/output apparatus to mix with and preheat the combustion air. Steam is created by the passing of the flue gas across a series of tube contained within the OTSG. The tubes are arranged in a combination counter-current/co-current configuration to provides for the minimization of the creation of solid deposits in the tubes.

REFERENCE TO PENDING APPLICATIONS

This application does not claim the benefit of any pending patent application.

REFERENCE TO MICROFICHE APPENDIX

This application is not referenced in any microfiche appendix.

BACKGROUND OF THE INVENTION

The present invention is generally directed toward an apparatus to create steam. More specifically, the present invention is directed toward a once through steam generator.

The prior art has many different types of steam generating systems and apparatus. These prior art systems and apparatus, however, are not the most efficient or effective. Additionally, these systems have a significant amount of solids deposition on the inner surfaced of the steam generator tubes. Additionally, the cost to erect these apparatus is typically very expensive. Accordingly, there is a need for an improved steam generator.

SUMMARY OF THE INVENTION

The present invention is generally directed toward a once-through steam generator (OTSG).

One aspect of the present invention discloses once-through steam generator having a steam generation apparatus in communication with a combustion apparatus and a combustion air input/output apparatus. Combustion air enters the OTSG through the air input/output apparatus and is then fed into a combustion apparatus to generate flue gas. The flue gas is then fed into the steam generation apparatus to generate steam. The flue gas is returned to the air input/output apparatus by way of a flue gas recirculation (FGR) stream where it can either be released from the system or mixed with new combustion air and recycled back through the combustion system. The steam that is created is then used with the recovery of oil from a reservoir.

One aspect of the combustion system portion of the present invention discloses a combustion air fan, a burner and a combustion chamber. The combustion air fan pulls combustion air through the air input/output apparatus through the burner and into the combustion chamber. When the combustion air passes through burner it is mixed with fuel to create a fuel/air mixture. This mixture combusts when it is inside the combustion chamber producing flue gas.

One aspect of the steam generator system portion of the present invention provides for the creation of steam through a once-through steam generation (OTSG) process. A series of tubes are arranged in a coiled configuration. Feedwater in introduced into the tubes through an inlet. Once the water has been converted into steam, the steam exits the tubes through an outlet. Flue gas is introduced into the steam generator system and passed over the tubes. Due to the temperature differential between the temperature of the feedwater and flue gas, the feedwater is converted into steam. The flue gas then exits the steam generator system portion through a flue gas recirculation stream where it is returned to the air input/output apparatus.

One aspect of the air input/output portion of the present invention provides for the in-flow of combustion air and an out-flow of flue gas. Combustion air enters the air input/output portion through an inlet/outlet opening and passes through an air control damper in to a combustion air duct. Once the combustion air passes into the combustion air duct, it is then introduced into the combustion portion of the present invention where it is converted into flue gas. Once the flue gas has heated the feedwater and has exited the steam generator system portion of the present invention, it passes through a flue gas recirculation damper and back into the input/output portion of the present invention allowing the flue gas to be recycled back into the combustion system.

Upon reading the included description, various alternative embodiments will become obvious to those skilled in the art. These embodiments are to be considered within the scope and spirit of the subject invention, which is only limited by the claims which follow and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an embodiment of the once-through steam generating inventive system described herein.

FIG. 2 is a schematic illustration of an embodiment of combustion system contained within the once-through steam generating inventive system described in herein.

FIG. 3 is a schematic illustration of an embodiment of steam generator system contained within the once-through steam generating inventive system described in herein.

FIG. 4 is a schematic illustration of an embodiment of air input/output system contained within the once-through steam generating inventive system described in herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description shows the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made for the purpose of illustrating the general principles of the invention and the best mode for practicing the invention, since the scope of the invention is best defined by the appended claims. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein are for the purpose of description and not of limitation.

Referring now to FIG. 1, shown is a schematic illustration of one embodiment of the present invention. Numeral 10 broadly denotes the overall process. Combustion air 12 enters the process through an air input/output apparatus 13 and is then fed into a combustion system 20 to generate flue gas 28. The flue gas 28 is then fed into a steam generation system 40 to generate steam 44. The flue gas 28 is returned to the air input/output apparatus by creating a Flue Gas Recirculation (FGR) stream 30. Depending on the heat needs of the process, the flue gas 28 is either recycled back through the combustion system 20 mixing with, and preheating, the combustion air 12 that is entering into the air input/output apparatus 13 or is release through the input/output apparatus 13. The steam 44 that is created is then used with the recovery of oil from a reservoir.

Having broadly discussed the overall process, numerous advantages attributable to the process are evinced. These include i) improved combustion efficiency due to the preheating of combustion air with the heat of recirculated flue gas that would normally go out the stack; ii) improved oil recovery from a reservoir through increased reliability of the steam generator; iii) enhanced steam generation due to a reduction in dissolved solids deposition on the inner surfaces of the steam generator tubes; iv) lower stack emissions of NOx and v) improved erection cost and vi) improved shipping costs due to a more compact combustion system or vii) any combination of these features.

Referring now to FIG. 2, an embodiment of combustion system 20 is shown in a more detailed schematic. In the embodiment shown, combustion system 20 is provided for the combustion of combustion air 12 into flue gas 28. A combustion air fan 22, a burner 24 and a combustion chamber 26 are provided for the system 20. The combustion air fan 22 is useful to pull combustion air 12 through the air input/output apparatus 13 and into the combustion system 20 and push the air 12 through the burner 24 and into the combustion chamber 26. The combustion air 12 passes through burner 24 where it is mixed with fuel to create a fuel/air mixture which then combusts within combustion chamber 26 producing flue gas 28.

The fuel, contained in any of air or oxygen mixture, may be selected from any suitable hydrocarbon fuel, non limiting examples of which include natural gas, bitumen, fuel oil, heavy oil, residuum, emulsified fuel, asphaltenes, petcoke, coal, and combinations thereof.

Referring now to FIG. 3, an embodiment of steam generator system 40 is shown in a more detailed schematic. In the embodiment shown, steam generator system 40 is provided for the generation of steam 44 through a once-through steam generation (OTSG) process. A series of tubes 46 in a coiled configuration are provided for this system 40. The tubes 46 have a feedwater inlet 41 and steam outlet 43. Feedwater 42 is introduced into tubes 46 through feedwater inlet 41 and pass through tubes 46. Flue gas 28 passed over tubes 46. Due to the temperature differential between the temperature of feedwater 41 and flue gas 28, feedwater 41 is converted into steam 46. Steam 46 exits the system 40 through steam outlet 43. Flue gas 28 is combined with flue gas recirculation stream 30 where the gas 28 is returned to the air input/output apparatus 13.

In this embodiment, tubes 46 are placed in a combination counter-current 48/co-current 50 configuration. This configuration provides for the minimization of the creation of solid deposits in the tubes. The tubes 52 which are part of the counter-current section 48 are cooler in temperature and make better use of the temperature difference between the flue gas 28 and the feedwater 42. The evaporation of feedwater 42 into steam 44 occurs in tubes 54 which are part of the co-current section 50. By having all the evaporation in the tubes 54 that are part of the co-current section 50, the water-steam is in placed in an up-flow which encourages proper flow through the tubes 46 and helps relieve steam bubbles that have formed within feedwater 42.

Referring now to FIG. 4, air input/output apparatus 13 shown is a more detailed schematic of the process according to one embodiment. In the embodiment shown, air input/output apparatus 13 is provided for in-flow of combustion air 12 and out-flow of flue gas 28. An inlet/outlet 14, an air control damper 16, combustion air duct 18 and a FGR control damper 56 are provided.

The combustion air duct 18 is in communication with the combustion system 20. Due to the negative pressure within the combustion air duct 18 created by the combustion fan 22, combustion air 12 enters the air input/output apparatus 13 through the inlet/outlet 14 and passes through the air control damper 16 and the combustion air duct 18 into the combustion system 20.

Once the combustion air 12 passes through the combustion system 20 and is converted into flue gas 28, the flue gas 28 passed through steam generator system 40 and enters into air input/output apparatus 13 and passes through the FGR damper 56. Depending on the heat needs of the combustion system 20, flue gas 28 is either recycled back through the system or released from the system. The amount of combustion air 12 and flue gas 28 that is introduced into the combustion system 20 can be controlled by the opening and closing of air control damper 16 and FGR control damper 56.

When the heat needs require less heat to the combustion system 20, FGR control damper 56 closes allowing flue gas 28 to escape through the air inlet/outlet 14. When the heat needs require more heat, the FGR control damper 56 opens to allow flue gas 28 to be drawn into the combustion air duct 18 via the negative pressure created by the combustion fan 22. When the flue gas 28 enters the combustion air duct 18, it mixes with combustion air 12 being drawn into the system through air inlet/outlet 14. Due to the heat of the flue gas 28, combustion air 12 is preheated prior to its entry into the combustion system 20. This preheating allows for more combustion efficiency.

By controlling the amount of combustion air 12 and flue gas 28 that is introduced into the combustion system 20, the amount of heat within the steam generator system 40 can be controlled. This in turn allows for the control of the amount of heat that is used for the creation of steam 44, which allows for a control of the amount of solid deposits within the inside of tubes 46 that is created during the evaporation process.

While embodiments of the present invention have been illustrated and described, such disclosures should not be regarded as any limitation of the scope of our invention. The true scope of our invention is defined in the appended claims. Therefore, it is intended that the appended claims shall be construed to include both the preferred embodiment and all such variations and modifications as fall within the spirit and scope of the invention. 

1. A once through steam generator (OTSG) for use in creating steam from feedwater, said OTSG comprising: an air input/output apparatus having an inlet/outlet to allow combustion air into said air input/output apparatus; a combustion apparatus in communication with said air input/output apparatus to allow said combustion air access therein, said combustion apparatus having a combustion chamber to combust said combustion air to create flue gas; and a steam generation apparatus having one or more tubes contained therein, said steam generation apparatus in communication with said combustion apparatus to allow said flue gas access therein and to heat said one or more tubes and in communication with said air input/output apparatus to allow flue gas to recirculate back into said air input/output apparatus and to mix with said combustion air, said each of said one or more tubes having an inlet and an outlet, wherein said feedwater enters inside each of said one or more tubes and is converted into steam by the heat differential caused by said flue gas and wherein said steam exits said one or more tubes through said outlet.
 2. The OTSG of claim 1, wherein said combustion apparatus comprising: a combustion air fan providing circulation to said combustion air; a burner being configured to deliver fuel gas to mix with said combustion air mixes; and a combustion chamber wherein said fuel gas/combustion air mixture combusts creating flue gas.
 3. The OTSG of claim 1, wherein said one or more tubes contained within said steam generator apparatus being further defined as follows: each of said one or more tubes having a combination counter-current/co-current configuration.
 4. The OTSG of claim 1, wherein said air input/output apparatus comprising: an inlet/outlet to allow combustion air into said air input/output apparatus; a combustion air duct providing a passage way for said combustion air to access said combustion apparatus; an air control damper between said inlet/outlet and said combustion air duct; and flue gas recirculation control damper in communication with said inlet/outlet and said combustion air duct, said flue gas recirculation control damper to direct flue gas into said combustion air duct to mix, and preheat, combustion air or into said inlet/outlet to allow said flue gas to exit said OTSG. 